Chip-to-chip copper direct bonding in no-vacuum ambient using (111) oriented nano-twinned copper

Jing Ye Juang*, Kai Cheng Shie, Yu Jin Li, Benson Lin, Chia Cheng Chang, King-Ning Tu, Chih Chen

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

In this study, we demonstrate the chip-to-chip copper direct bonding by using (111) oriented nano-twinned copper in N2 ambient, without vacuum. A well bonded interface in the Cu-to-Cu joint was identified by the focus ion beam (FIB) microstructure observation. The secondary electron images (SEI) showed a void-less bonding interface within the bonded Cu joint. In addition, a die shear test was conducted. The test result revealed that the Cu joint has a robust bonded Cu structure due to its high value. The shear strength is more than 100 MPa. There is nearly twice strength value higher than the traditional SnAg solder joint (64 MPa). In addition, the scanning electron microscope (SEM) image showed the joint fractured in a ductile manner. Besides, we also performed the resistance measurement by using Kelvin probes on the bonded chip-to-chip test vehicle. The result showed 4.12 mΩ in single joint resistance and 4.26 × 10-8 Ωcm2 in contact resistivity. More than 30% resistance reduction has been confirmed as compared to the traditional SnAg solder joint (6.32 mΩ). Moreover, for further post annealing process on the bonded test vehicle, we can further reduce the joint resistance by the value of 2.9 mΩ. It approaches the value of bulk Cu. The evidences revealed that the Cu-to-Cu joint is superior to the traditional SnAg solder. In last, the chip-to-chip copper direct bonding by using (111) oriented nano-twinned copper in N2 ambient was achieved.

Original languageEnglish
Title of host publication13th International Microsystems, Packaging, Assembly and Circuits Technology Conference, IMPACT 2018
PublisherIEEE Computer Society
Pages101-103
Number of pages3
ISBN (Electronic)9781538656150
DOIs
StatePublished - 24 Jan 2019
Event13th International Microsystems, Packaging, Assembly and Circuits Technology Conference, IMPACT 2018 - Taipei, Taiwan
Duration: 24 Oct 201826 Oct 2018

Publication series

NameProceedings of Technical Papers - International Microsystems, Packaging, Assembly, and Circuits Technology Conference, IMPACT
Volume2018-October
ISSN (Print)2150-5934
ISSN (Electronic)2150-5942

Conference

Conference13th International Microsystems, Packaging, Assembly and Circuits Technology Conference, IMPACT 2018
CountryTaiwan
CityTaipei
Period24/10/1826/10/18

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